Ultrasonic sensing systems provide an efficient and effective method of distance detection. These sensors require the use of a transducer as an ultrasonic transmitter to produce ultrasonic signals. These signals are propagated through a sensing medium and reflected by objects, in particular at a boundary surface of medium and object, at which the sonic speed changes. The same ultrasonic transducer may be used as an ultrasonic receiver to detect returning signals. Ultrasonic distance sensing systems are popular in vehicle application to detect the distance between vehicle front and/or rear and obstacles. The sensing medium is air. Several transducers are capable of accomplishing this function including such as piezoelectric transducers.
Ultrasonic transducers have been designed to have very good long range detection capabilities. In designing these sensors, it was always necessary to maximize the Q value of the transducer and minimize the frequency of operation. High Q amplifies the returning signal, and low frequency serves to reduce the attenuation of ultrasound in air because attenuation is a function of frequency. These prior art sensors, however, do not display the short range sensitivity provided by the present application.